Such band-feeding devices are, for example, used to guide an elongated band or strip of sheet metal intermittently to a punch. In the known band-feeding devices, the pressure load of the movable clamping claw is carried through a flexible hose. This has the disadvantage in situations where the installation volume of the band-feeding device is enlarged; furthermore moving machine parts or persons can get caught on the flexible hose sections. Finally, a rupturing of the hose connections are always a risk for the operating safety.
Therefore, the present invention provides a further development of the known band-feeding device in such a manner that the hose connection to the movable clamping claw can be omitted.
Starting out from the known band-feeding device, this purpose is inventively attained by providing one of the guide rods for one of the clamping claws with a pressure medium channel therein, which guide rod extends with its free end section sealed against the flow of fluid into a blind hole of a further clamping claw, to which hole the clamping structure of the further clamping claw is in fluid connection.
The inventive band-feeding device has very compact dimensions and smooth limiting surfaces for effecting an adjustment of the stroke. It can therefore also be installed well near moving machine parts and under narrow space conditions. The pressure medium supply for the moving clamping claw is protected against outside influences. Also the axial dimensions of the band-feeding device can be kept small, since no consideration needs to be given to small curvature radii of hoses.
By connecting the valve block directly on the housing, which valve block controls both the tensioning movements and also the relative movement between the clamping claws, the hose connections can be eliminated.
A further development of the invention includes a provision wherein the stroke of the relative movement between the two clamping claws can be adjusted in a simple manner.
This adjustment occurs preferably by using a threaded member. In this case, one can adjust from an external source and with great precision the stroke by counting the rotations of a shank portion of a stop and by reading the angle position of the shank, in practice easily by using a fine thread with an exactness of better than 0.05 mm.
A further improvement over known band-feeding devices is the provision that the movable clamping claw smoothly decelerates as it approaches its end positions and also smoothly accelerates again away therefrom. With this it is assured that an undesired slip does not occur between the jaws of the clamping claw and the band to be conveyed.
The end damping position can be adjusted in order to allow for a different size stroke, different conveying speeds through a suitable change of the pressure medium load of the working cylinder which creates the relative movement of the clamping claws and different friction conditions.